Well screening method and device therefor



Aprll 25, 1961 M. K. MILLER ET AL WELL SCREENING METHOD AND DEVICE THEREEDR 5 Sheets-Sheet 1 Filed Feb. l, 1957 INVENTORS April 25, 1961 M. K. MILLER ET AL 2,981,332

WELL SCREENING METHOD AND DEVICE THEREEDR Filed Feb. 1, 1957 s sheets-shee1 2 Airman/5y April 25, 1961 M. K. MILLER ET AL 2,981,332

WELL SCREENING METHOD AND DEVICE THEREFOR Filed Feb. l, 1957 5 Sheets-Sheet 3 TTOZ/l/E/V WELL SCREENING METHD AND DEVICE THEREFOR Filed Feb. 1, 1957, Ser. No. 637,687

Claims. (Cl. 166-12) This invention relates to the introduction of well fiuids such as 0.1 and water from a formation into a Well, while preventing accumulation of particles of earth and sand in the Well. The invention is particularly concerned with procedure for screening earth and sand particles against introduction into a well with the well uidand apparatus for this purpose.

It is known to mount filter elements on perforated liners which are inserted in oil wells. Frequently, however, a condition of running sands or cave-ins is encountered in a well, which causes the liners to stick, and also causes the introduction of sand and other particles particularly into the annulus between the liner and the Wall of the bore, and also into the oil well string. The main object of this invention is to provide a screening element around the perforated liner so that it fills the annulus between the wall of the well and the liner to prevent the introduction or the accumulation in said annulus of earth and sand which would block off the liner and cause the difficulties previously defined, but which would be porous to permit the movement of oil through the screen and into the liner and up the tubing of the oil well.

The invention is directed to the use of an expansible screening element which surrounds the liner and has an outside diameter which permits the introduction of theliner through the casing and into the open portion of the hole, and when the liner is in position'said element can be permitted to expand to fill the entire annulus. For this purpose any suitable resilient material which can be compressed and expanded can be utilized as the screening element. A specific form of such screening element can be, for example, a circular tube or mat of glass fiber, mineral wool, metal filament such as metal wool, or other similar fibrous or foraminous material, including elastomers, which can be compacted around the outside of the liner and held against its outer periphery to permit the introduction of the wrapped liner into the casing. The liner is perforated at the place where the mat is positioned. A constricting element is positioned about the screening element or screen to hold it in compression. When the liner is placed in position in the well, the constricting element is released, so that the mat can expand due to its resiliency.

It has been determined that fiber glass mats or batts can be compacted under pressure suicent so that the fibers will not be broken down, and when the compacting forces are removed the mat can expand as much as five times its compacted thickness. For this purpose we may employ compactible and resilient glass fiber batts. The resiliency and compactibility of the glass fiber structures or batts can be varied to meet any specific requirements, e.g., by varying the orientatfon of the glass fibers. If desired, a relatively thin, compact, fiberglass mat of increased screening ability may first be placed tightly around the perforated liner and a resilient expansible fiberglass batt positioned about said mat. Alternatively, layers of'tiberglass material of enhanced Screening ability tetes. @taff may be incorporated in the expansible fiberglass batt, or"

about the outer periphery of the fiberglass batt to expand with the batt and make contact with the wall of the well bore when constricting element is removed.

The filaments of the glass fiber mats or batts which may be employed are preferably coated with a resin to decrease the brittleness of the glass fibers. Resins which can be used for this purpose include, for example,v

phenolic resins such as phenol-formaldehyde and phenolfurfural, methyl mathacylate, and the like, as known in the art. The resins utilized for bonding the glass fibers should be resistant to oil, water and acids such as hydrochloric, and should not decompose at the well tempera-V ture encountered.

As specific constricting elements for the screen which may be employed, we can wrap the mat of batt forming troduction of a go-devil, which slides over the pipe ony which the slotted liner is suspended, and thus releases the constricting elements to permit the mat to expand. p

According to the invention the screening element, e.g.,`

a res n bonded fiberglass batt, is positioned about a per-i forated liner and is compressed by the constricting'ele-4 ment. The tool is passed through the well bore, generally through the casing therein, to the production zone.

The constricting element is then released in the afore-` mentioned manner, the resiliency ofthe screening element permitting it to expand partially to the face of the wall of the well bore. The screening element thus takes a position against the well wall and is still funder somez compression while against the wall. In this expandedl position, the tubular screening element completely fills the annulus between the wall of the well and the liner on` whch the screen is mounted. The resiliency of the" screening element maintains'it in contact with said` Wall during the producing operation, and the differential pressure between the fluid passing into said elementland the opposite force due to resiliency of the screen, is controlled so that it is insufficient to compressandforcey the screen element or mat away from the wellwall.

Thus, the screening element in its operative position completely closes of the annulus between the liner and well wall so that sand and earth particles adjacentthe wall cannot fall/into the annulus, and hence' the outer.

surface of the resilent tubular element functions to screenI off such particles While permitting the fiuid to pass through to the liner. Any minor portion of sand particles.

which may be carried through the screening element are usually deposited within the resilient screen and are notv carried into the liner. However,.it is to'be noted that` the resilent screening element functions essentially to'- block particles of sand at the wall of the bore at the outer contact surface of the screening element,` and functions only to a minor degree, if at all, as a filter.

Where the constricting means for the screening ele-- ment is a sheath or is in the form of bands, of a metal such as zinc, magnesium, or aluminum, a mineral acid such as hydrochloric acid can be used to disintegrate the` constricting member, a conventional inhibitor being f added to the acid to prevent corrosion of the steel well equipment. Inhibited acids of this type which can be used are those conventionally employed in acidizing wells. Where the constricting means is a plastic sheath or bands made of plastic, e.g.,4 a cellulosic or a vinyl resin, an organic solvent'which will readily dissolve the plastic is'l Paimeld Apr. A2s,v 19st.

employed. For example, in the case of cellulose acetate butyrate, the solvent may be a ketone such as acetones, and in the case of polystyrene the solvent may be an aromatic or chlorinated. hydrocarbon. The plastic employed should be inert toA oil. and. preferably also inert to acids; t

We may also employ as the constricting means a sheath or bands composed of a material which will disintegrate by heat to release said means. Thus, we may employ certain alloys which will melt or disintegrate by contact with hot Water or hot oil, preferably bismuth alloys. In. this case, the temperature required for melting the particular alloy employed should be higher than the temperature of that portion ofV the well through which the liner passes and in which it is positioned, so that the constricting member will not melt or disintegrate before it is positioned at the desired location in the well.

In the above cases,l the screening element employed should be constructed of a material which is inert to the means employed for releasing the constricting means. Thus, where an acid is employed for this purpose, the screening element should be inert thereto, and when an organic solvent is utilized for disintegrating said means, the screen should be composed of a material inert thereto. Further, the `screening element should` be inert to oil. Also, said element should be resistant tothe temperatures encountered in the well. Fiberglass batts are preferred as.. the screening element because of its compactibility, resilience, and resistance to heat and chemicals.

Alternatively the constricting element or elements may be released by. mechanical rather than chemical means. In this case, forexample, a metal sheath may be employed as the constricting means, such sheath being connected mechanically to a structure, which, on actuation from the well surface, pulls the sheath up over the enclosed. screening element, to permit the latterV to expand to the. well bore in the manner previously described.

The invention will be more clearly understood by reference to theV accompanying drawings wherein:

Fig. l is an elevational view, partly in section, of one form of the invention device, located inposition in a well bore;

Fig. 2 is Eig.. l;

Fig; 3 is a view similar to Fig. l, showing the screening element in expanded position against the wall of the bore;

F Fig. 4 is a horizontal section taken on line 4-4 of ig. 3; e

Fig. 5 shows a modificationV of the constricting element for the expansible screen;

a horizontal section takeny on line 2 2 of Fig. 6 is a view similar to Fig. 1,. showing another embodiment of our device;

Fig. 7 is a horizontal section taken on line 7--7 of Fig. 6; and

Fig. 8 is a horizontal section taken on line 8-8 of Fig. 6.

Referring to Figs. 1 to 4, the tool comprises a liner 10 threadably connected at its upper end 12 to a collar 14 carried at the lower end of a pipe fitting 15 which is joined at its upper end to a liner pipe 16. Mounted above the collar 14 is a collar hanger indicated generally by the numeral 18, said collar hanger being of a conventional type, eg., as manufactured by'S. R. Bowen & Coi., Lane Wells, and other vendors. The liner hanger shown comprises an axially movable collar 22 mounted about fitting 1S, the collar 22 being attached by means of a number of` connectors to a series of grippers 24. Said grippers when forced upward by a spring 26 mounted about fitting 15v between collars 14 and 22, pass over a' conical portion28 of pipe fitting 15 and onto an enlarged cylindrical upper portion 30 of fitting 15 at the tool joint, causing said grippers to expand outwardly into gripping contact with the wellcasing 32, as seen in Fig. 3. The

structure of the liner hanger 18 forms no part of the instant invention.

The liner 10 is closed at its lower end 34 and has distributed about the major portion of its surface a series of perforations 36 such as are conventional in slotted liners. A pair of spaced supporting rings 33 are mounted about the outer periphery of the liner 10 adjacent the upper and lower ends of the perforated portion of the liner. Between rings 38 is supported a tubular glass fiber mat or batt 40 covering the perforated portion of the liner. Preferably, the screening element or mat 40 can be connected to the outer periphery of the liner 10 by a suitable cement applied between their surfaces and preferably covering only narrow peripheral portions near the top and bottom of the inner surface of the screening element and adjacent surface areas of the perforated liner, as indicated at 41, care being taken that said cement does not cover the perforations 36. The cement should be one which will withstand temperatures up to say about 250 F. or more, is insoluble in water and crude oil, and which will be inert to the acid or solvent used to disintegrate the constricting element, c g., sheath 42, where removal of said constricting element is to be accomplished by chemical means. Such cement can be employed, together with the supporting rings 38, or the cement can be used alone without such rings, or the rings alone can be used to support the screening element 40 on the liner 10. Cements which can be used for this purpose are well known in the prior art, and include, for example, cements of the phenol-formaldehyde or ureaformaldehyde type, and the like.

The rnat 40 is compressed by a cylindrical metal sheath 42, eg., of zinc, magnesium, aluminum and the like, which fits tightly about the mat 40. It will be seen in Fig. l that the outside diameter of the constricting metal' sheath 42 is slightly less than the internal diameter of the well casing 32, permitting passage of the liner through said casing.

When the tool is introduced through the casing 32 into the open portion of the well bore 44 adjacent the producing zone 46, the liner hanger 18 is actuated by means of a tool in a well known manner, to release the spring 26 and to cause the grppers or slips 24 to contact the inner surface of the casing 32. The weight of the tool causes the grippers to tightly grip the inside wall of the casing 32, as seen in Fig. 3, to hold the liner 10 in position below the casing. An acid solution such as inhibited hydrochloric acid usually employed in acidizing wells is then circulated down into the annulus 48 between the metal sheath 42 and the bore 44, causing the metal sheath 42 to disintegrate. Removal of sheath 42 results in partial expansion of the fiberglass screeningmat 40 into contact with the wall 44 of the well bore', as seenA in Fig. 3, and iilling the annulus 48.

Thus, for example, a screen or mat such as the liberglass batt 4u, having an initial thickness of about 2" under full compression, may expand say l", or half the original thickness, when it makes contact with the bore wall 44. The mat 40 in the position shown in Fig. 3 has sulicient remaining resiliency or outwardV force so that it is not pushed away from the wall by the pressure of the iiuid passing from the producing zone 46 into the screen 4B. The maintenance of the screening element 4t) in snug contact with the wall of the bore during the operation of the well prevents introduction of sand and earth particles into the annulus 43k between the wall 44 of the well and liner 10. Also, this feature prevents running sands and cave-ins of the earth and sand form' ing the walls of the bore.

The screening element or mat 40 remains in the expanded positcn shown in Fg. 3 throughout the period of production of the well, or until after `an extended period,

the. screening element may become clogged and require replacement. After release of the grippers 24 from the casing, inv known manner, sothat the linear hanger again assumes the position shown in l, the liner 10 carrying `the used screening element 40 can be lifted through the liner pipe 16 to the surface of the well. Although in expanded position, the mat can be pulled through the casing and removed from the well.

In Fig. is shown a modified form of constricting means for maintaining the screen 40 in compression while the liner is introduced through the casing to its position adjacent the producing zone, as described above. In this modification, a series of spaced metal, e.g., magnesium bands 50 are compacted about the outer periphery of the glass fiber mat 40 to hold it under compression as in the case of the metal sheath 42, the outer diameter of the bands 50 being somewhat less than the inside diameter of the casing 32, to permit the wrapped liner 10 to pass freely through the casing. When the liner and mat 40 are in proper position in the well adjacent the producing zone, an inhibited hydrochloric acid solution of the type used for acidizing wells is introduced into the annulus 48 between the wrapped liner 10 and the well bore, causing the metal bands 50 to disintegrate and. dissolve, thus permitting the mat 40 to expand into tight engagement with the wall of the bore to fill said annulus, as peviously described.

In Figs. 6 to 8 is shown still another modified form of constricting means for holding the screening element in compression about the liner 10, said constricting means being mechanically removable. Here a metal cylindrical sheath 52 holds the fiberglass mat 40 sufficiently compressed to permit passage of the liner 10 carrying said mat, down through the casing 32. Integrally connected to the upper end of the metal sheath 52 are four lift straps 54, the straps being equally spaced circumferentially about said sheath. The straps 54 extend upward longitudinally of the tool and are integrally connected at their upper ends to a lift collar 56 disposed above tool joint 30, said collar 56 having a pair of diametrically opposed lugs 58 to which cables 60 are attached by means of fasteners 62. It will be seen that the sheath 52 has an outer diameter less than the inside diameter of casing 32, and that lift straps 54 and collar 56 are spaced from the inner wall of the casing, permitting liner 10, its encased screen 40, and the straps 54 and collar 56 to pass down through the casing.

When the liner 10 and elementV 40 thereon are placed in position below casing 32, cables 60 are pulled upwardly, lifting collar 56 and straps 54, and in turn lifting the sheath 52 to cause it to slide upwardly over and out of contact with the fiberglass mat 40. This permits the mat 40 to expand part way into tight engagement with the wall of the bore, as described above.

Instead of employing a metal sheath 42 or metal bands 50, we can use a plastic bag or sheath, or we can employ plastic bands or cords to compress the screen element, said plastic material being, for example, polystyrene. In these instances the plastic sheath or bands can be dissolved or disintegrated by means of a suitable solvent such as an aromatic hydrocarbon. We can also use a sheath or bands composed of bismuth or bismuth alloys, and disintegrate such sheath or bands by the application of heat. Suitable alloys are, for example, the following:

Table Composition in parts by weight Melting Alloy pgt,

Tin Lead Bismuth cadmium 4 s 15 14o-16o 2s 25 50 203 2 2 5 221 24.6 28.1 5o 230 24. s 22. 1 53. 1 25o Where the well temperature is relatively low, we may V.use a lower melting bismuth alloy such as alloy A or B in constricting the above sheath or bands, and introduce" hot water into the annulus between the wrapped liner and well bore, for melting the alloy to remove said sheath or bands and cause the screen to expand to the wall of the bore. When the well temperature is higher, we may use the higher melting alloys C,`D or E, and melt the alloy by circulating hotoil in said annulus to disintegrate the sheath or bands. It will lthus be understood that not only can we employ any suitable expansible screening element, but we can employ any suitable form of restraining means to maintain said element in compressed condition for passage through the well bore or casing therein to the desired location in the well, and we can also utilize acids, solvents, heat or mechanical means to disintegrate or remove said restraining means.

While our device is especially designed for use in an uncased portion of a well, that is, in a zone of the well in which the walls are formed by natural earth formations, as described above, our device also has application in a well bore adjacent a production zone wherein the well wall adjacent said zone has been lined with casing cemented in place and gun perforated in known manner to permit passage of fluids from the formation through the casing and into the well. For example, casing 32 may be extended down to the bottom of the well as seen in Fig. 1, and cemented in along production zone 46 by application of cement in an annulus between the outside of the casing and the well wall 44, and the casing and cement adjacent zone 46 gun perforated. When the screening element or mat 40 is caused-to expand by disintegration or removal of the sheath 42 or bands 50, the

mat will expand into engagement with the casing, holding back sand and earth particles which pass with the well fluids through the casing perforations, and preventing such particles from entering the annulus between the casing and the liner.

From the foregoing, it is seen that the invention provides a facile method and novel apparatus, which permit removal of oil, water or other fluids from the production zone of a well, and passage of such liuids into the well bore or perforated liner usually employed, without causing particles of sand and earth to be introduced into the annulus between the bore and the liner, and thus interfering with the iiow of iiuids into the well. Our method and device have additional advantages, for example, the expansible screening element when partially expanded and compressed against the earth forming the Wall of the bore, helps to support the wall against collapse while at the same time being insufficiently compressed against said wall so that the well fluids can pass into and through the screening element and into the liner. Further, our device reduces the amount of earth particles introduced into the liner itself.

While we have described particular embodiments of expandable radially a relatively substantial amount on removal of said constricting means and means securely holding said screening element on said tube after said constricting means is removed. Y

2. A device for insertion in a well bore, which comprises a perforated tubular liner, an expansible tubular resilient screening element connected to said liner and snugly surrounding the perforated portion of said liner, and a constricting means engaging said element and maintaining said element under compression to thereby reduce thediameterof'v said element, said constricting means being removable while said element is in said well bore, Saidl element being expandable radially a relatively subsantial amount at least equal to half the original thickness of said element into snug engagement with the wall of said bore on removal of said constrictingmeans, to therebyffill the annulus between said liner and the wall of said bore.

3. A process which comprises compacting an expansible resilient foraminous screening medium with a constricting member surrounding and in tight Contact with said screening medium, introducing said compacted screening medium into a well bore, removing said constricting member and causing said screening medium to expand radially a relatively substantial amount into compressive contact with the wall of said well bore to form aforaminous barrier against said wall.

4 A device for insertion in a well bore, which comprises a perforated tubular liner, an expansible tubular screening element connected to said liner and snugly surrounding the perforated portion of said liner, and a removable constricting means engaging said element and maintaining said element under compression to thereby reduce the diameter of said element, said element being partially expandable into snug engagement with the wall of said bore on removal oi said constricting means, to thereby fill the annulus between said liner and the wall of said bore, said constricting means being composed of a metal which is readily fusible, said means being removable at elevated temperature on the application of heat.

5. A device as defined in claim 4, wherein said metal is a bismuth alloy.

6 A device as defined in claim 2, wherein said cons tricting means is composed oi' a plastic material, said means being removable by treatment with a solvent for said plastic.

7. A device as defined in claim 2, wherein said fibrous mat is a iiberglass batt and said constricting means is in the form of a material which can be disintegrated by a fluid which attacks said material.

8. A process which comprises compacting an expan sible resilient foraminous screening medium with a surrounding ring of a material which is disintegrated by treatment with a liquid corrosive to said material, introducing said compacted screening medium into a well bore, passing a liquid corrosive to the material of said ring into said well bore into contact with said ring, said liquid corroding and disintegrating said ring, causing said screening medium to expand radially a relatively substantial amount into compressive contact with the Wall of said well bore to form a foraminous barrier against said wall, whereby iiuid from a formation adjacent said wall vpasses into and through said foraminous barrier, and is introduced into a central zone ofsaid bore.

9. A device for insertion in a well bore, which comprises a perforated tubular liner, an expansible tubular resilient screening element connected to said liner and snugly surrounding the perforated portion of said liner, and a removable constricting means engaging said element and maintaining said element under compression to thereby reduce the diameter of said element, said element being partially expandable into snug engagement with the wall of said bore on removal of said constricting means, to thereby fill the annulus between said liner and the wali of said bore, said constricting means being in the form of a sheath completely surrounding said screening element.

10. A device for insertion in a well bore, which comprises a perforated tubular liner, an expansible tubular resilient screening element connected to said liner and snugly surrounding the perforated portion of said liner, and l a constricting means engaging said element and maintaining said element under compression to thereby reduce the diameter of said element, said element being expandable radially a relatively substantial amount at ,least equal to half the original thickness of said element into snug engagement with the wall of said bore on re- Ymoval ofsaid 'constricting means, to thereby iill the annulus between said liner and the wall of said bore, said constricting means being: in thefform of a plurality of spaced bands surrounding said screening element.

11. A device for insertion in a well bore, which comprises a tube, a perforated tubular liner connected to. the lower end of said tube, an expansible, resilient, foraminous tubular fibrous mat supported on and snuglyy Surrounding the perforated portion of said liner, and a removable const'ricting means engaging said screening element and maintaining it under compression to thereby reduce the diameter of said element, said screening element being partially expandable into snug compressive engagement with the wall of said bore on removal of said constricting means to thereby iill the annulus between said liner and the wall of said bore, said fibrous mat being a iiberglass batt and said constricting means being in the form of a bismuth alloy which can be disintegrated by heat at a modestly increased temperature.

l2. A process which comprises introducing into a well bore an expansible, resilient, foraminous screening medium carrying a constricting element holding said medium in compression, maintaining said resilient screening medium under compression out of contact with the wall of said bore during introduction of said screening medium into said well bore to a selected location therein, removing said constricting element and causing said medium to Yexpand radially a relatively substantial amount into compressive contact with the wall of said well bore to form a foraminous barrier against said Wall, and maintaining said screening medium in contact with said wall during passage of iiuid from a formation adjacent said wall into and through said foraminous barrier.

13. A process which comprises introducing in a well bore a perforated liner carrying an expansible, resilient, permeable screen having thereon a constricting element holding said screen in compression, maintaining said resilient screen under compression during introduction of said screen into said well bore to a selected location therein, removing said constricting element and causing said screen to expand radially a relatively substantial amount into snug engagement with the wall of said well bore while maintaining said screen in position on said liner, the volume of said screen increasing without changing the internal diameter thereof adjacent said liner, forming a foraminous barrier against said wall and maintaining s aid screen in contact with said wall during pasage of fluid from a formation adjacent said wall into and through said foraminous barrier.

14. A process which comprises placing a constricting element about an expansible, resilient, permeable screen carried on the outer periphery of a perforated tube, to hold said screen in compression, introducing said screen and tube into a well bore, maintaining said permeable screen under compression, out of contact with the wall of said well bore on introduction of said screen into said well bore to a selected location therein, removing said constricting element to release said screen and permit expansion thereof radially a relatively substantial amount into snug engagement with the wall of said well bore while maintaining said screen in position on said tube, the volume of said screen increasing without changing its internal diameter adjacent said tube, forming a foraminous barrier against said wall and maintaining said screen in contact with said wall during passage of fluidv from a formation adjacent said wall into and through said foraminous barrier.

i5. A device for insertion in a well bore, which comprises a tube, a perforated tubular liner connected to the lower end of said tube, a self expansible, resilient, foraminous tubular ibrous mat supported on and snugly surrounding the perforated portion of said liner, and a constricting means engaging said screening element and maintaining it under compression to thereby reduce the diameter of said element` and maintain it in an inoperative condition, said constricting means being removable 9 while said element is in said well, said screening element being self expandible into operative position on removal of said constricting means, and means securely holding said fibrous mat on said tube after said constricting means is removed.

References Cited in the file of this patent UNITED STATES PATENTS 572,848 Wheeler Dec. 8, 1896 10 Archer May 11, 1909 Kneuper Sept. 14, 1909 Byerly Oct. 26, 1926 Vietti et a1.a July 25, 1939 Blood Jan. 1, 1952 Carr et al Sept. `23, 1952 West Oct. 14, 1952 

